Conventionally, as the radio communication method and the radio communication apparatus, for example, there are those described in JP-A-2003-229869. FIG. 42 is a diagram showing the radio communication method described in JP-A-2003-229869. With the radio communication method, radio communication apparatuses communicate with one another directly without a control station in the radio network.
In FIG. 42, the radio communication apparatuses transmit management information including timing information of the start position of their reception, reception window information, and reception cycle information, at specified time intervals (M1 to M4). The other communication apparatuses, which can receive this management information, store reception timing, reception windows, and reception cycles in association with communication apparatus numbers of the corresponding radio communication apparatuses. At the time of transmission of information, the other radio communication apparatuses find the reception start positions of the corresponding radio communication apparatus from the reception timing, the reception windows, and the reception cycles of the radio communication apparatus to be communicated and transmit the information according to this timing.
Note that during a management information exchange area (hereinafter referred to as “beacon period”) (C1, C5), all the radio communication apparatuses transmit management information during the beacon slots of the respective radio communication apparatuses and so exchange the management information.
However, in the conventional method, since the beacon periods are at fixed times, a radio network system, in which it is unknown in advance how many beacons are transmitted, has problems described below. When radio communication apparatuses actually belonging to this radio network system have nodes far fewer than the number of nodes assumed in advance, there is long idle time in the beacon periods and communication efficiency is low.
Since all the nodes continue to operate in a reception waiting state in the time of the beacon periods, a beacon period longer than necessary consumes excess power. Thus, waste of power consumption increases.
Moreover, when another radio network system which adopts the same radio communication format is present near the radio network system in question, the longer the beacon period is, the more likely it is that beacons or data communication of the two radio network systems conflict with one another.
On the other hand, when the number of apparatuses joining this radio network system is larger than the number of nodes assumed in advance, empty slots of the beacons are insufficient and some of the radio communication apparatuses cannot participate in the radio network system.